1. Field of the Invention
The present invention relates to a vaporizer for vaporizing liquid, a fuel cell having the vaporizer, and a vaporizing method.
2. Description of the Related Art
In recent years, fuel cells receives attention as clean power supply having high energy converting efficiency, and the fuel cells are widely introduced commercially such as fuel cell automobiles and electrified housings. Studies are carried out for commercial viability of the power supply by the fuel cells also in a portable electronic equipment such as cellular phones and notebook personal computers in which research and development of downsizing are pursued abruptly.
Fuel cells are classified into two types, i.e., a reforming type and a fuel direct type. The reforming type is a type in which hydrogen is produced from fuel and water using a reforming device, and the produced hydrogen is supplied to a fuel cell like the reforming of water vapor. In the fuel direct type, fuel and water are not reformed, and they are supplied to a fuel cell. Generally, fuel and water are stored in the form of liquid, and the fuel and water are vaporized and then, a mixture of the fuel and water is supplied to the reforming device. Therefore, a vaporizer for vaporizing fuel and water is required, and research and development concerning such vaporizer are pursued together with development of the fuel cell (see Japanese Patent Applications Laid-open Nos. 2004-47260 and 2001-263649 for example).
If such a vaporizer is made compact, since the flow rate is small, fuel is easily heated excessively. Therefore, fuel is irregularly bumping, liquid drop is mixed in the vaporized liquid and it is difficult to control the stable vaporization. When a mixture of a plurality kinds of liquid having different boiling points such as fuel and water is vaporized, influence of bumping is serious, and it is more difficult to control.
When a post reforming device or a fuel cell is disposed, such an instable factor makes reforming performance by the reforming device or electric power generating performance by the fuel cell instable.